Advanced design of UV waveplates based on nano-structured thin films

Grinevičiūtė, Lina; Buzelis, Rytis; Andrulevičius, Mindaugas; Lazauskas, Algirdas; Selskis, Algirdas; Drazdys, Ramutis; Tolenis, Tomas

doi:10.1117/12.2273787

Cited by 2 publications

(2 citation statements)

References 11 publications

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“…In contrast, mesomorphic ceramics are macroscopically ordered solids with morphologies intermediate between isotropic materials and single crystals and include sculptured inorganic thin films fabricated via glancing angle deposition (GLAD). However, GLAD must be performed under precise conditions to control defects and thus is limited to small areas. − Soft materials like polymers and liquid crystals can be inexpensively processed into large area waveplates; however, they lack the thermal stability and photostability desired for high power laser applications. Thus, there is a long-standing need for cost-effective, inorganic waveplates over large areas.…”

Section: Introductionmentioning

confidence: 99%

Mesomorphic Ceramic Film Fabricated via Blade Coating of a Lyotropic Nematic Liquid Crystal for High-Power Lasers

Cheng

Chen

Anthamatten

2022

ACS Appl. Nano Mater.

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Mesomorphic ceramic films are fabricated over large areas by blade coating of a lyotropic nematic sol of zinc oxide nanorods. Upon calcination to remove organics, continuous monodomain films with a uniform thickness result as transparent ceramics, exhibiting uniform birefringence over centimeter dimensions. At low blade-coating velocities, the dry film thickness varies inversely with the coating velocity, whereas at high coating velocities, it increases with increasing velocity as prescribed by the Landau–Levich theory. The thickness–velocity scaling in the Landau–Levich regime depends on the shear-thinning behavior of the lyotropic nematic sol. The optimization of the coating process for the minimization of optical defects leads to transparent monodomain films that exhibit a uniform in-plane birefringence of 0.032 ± 0.002 from 580 to 1690 nm. After calcination, the resulting mesomorphic ceramic films span large areas (3.5 cm × 2.5 cm), are optically transparent with uniform thickness (0.60 ± 0.03 μm), and exhibit smooth surface finish with an average surface roughness of 20 nm. The alignment of zinc oxide crystallites along the coating direction within mesomorphic ceramics is confirmed by X-ray diffraction texture analysis and scanning electron microscopy imaging. As explained by the effective medium theory, the measured in-plane birefringence of 0.118 ± 0.003 is primarily contributed by form birefringence over intrinsic birefringence of zinc oxide in mesomorphic ceramics. The reported approach to highly ordered mesomorphic ceramics directly from lyotropic nematic sols, avoiding the gel state, could be generally applicable to other mineral liquid crystals, thereby benefiting the manufacture of optics for high-power lasers.

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Section: Introductionmentioning

confidence: 99%

Mesomorphic Ceramic Film Fabricated via Blade Coating of a Lyotropic Nematic Liquid Crystal for High-Power Lasers

Cheng

Chen

Anthamatten

2022

ACS Appl. Nano Mater.

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“…Due to their optical anisotropy, mesomorphic ceramics are under consideration as alternative waveplate materials. [13][14][15][16][17] Unlike inorganic single crystals processed into conventional waveplates, our group has recently developed a mesomorphic ceramic film that can be fabricated over large areas by blade coating a lyotropic nematic sol followed by calcination of the resulting oriented nanoparticle assembly. [13] Birefringence of the calcined films is attributed mainly to form birefringence originating in the anisotropic packing of rods with interstitial pores rather than intrinsic birefringence of the nanocrystal.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Trade‐off between Optical and Mechanical Properties during Constrained Sintering of Mesomorphic Ceramic Films

Cheng

Zhang

Chen

et al. 2023

Advanced Optical Materials

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Robust, transparent, and birefringent inorganic films are demanded for polarization control of high‐power lasers. While single crystals or films obtained via glancing angle deposition exhibit desirable optical properties and laser damage resistance, these methods are limited by cost and scalability. Mesomorphic ceramics as inorganic solids with liquid crystalline superstructure offer appealing transparency and birefringence but lack mechanical robustness due to their high porosity. Here, the effect of sintering on optical and mechanical properties of mesomorphic ceramics is evaluated. Films prepared by blade coating are sintered under varying conditions. Constrained sintering accomplished crystallite growth, densification, and morphological changes including necking as well as cracking while preserving the crystallographic orientation. The extent of sintering as a function of thermal treatment is quantified by morphology, surface area loss, and crystallite growth. Moreover, activation energies for surface diffusion and grain growth are estimated by surface area analysis and X‐ray diffraction peak narrowing, respectively. After sintering, birefringence decreases while Young's modulus and hardness improve as the film densifies. Upon partial sintering, mesomorphic ceramics retain transparency, high birefringence, and enhanced modulus. Laser‐induced damage threshold is measured as well. The reported results represent an important step toward the assembly and sintering of robust waveplates with high laser damage resistance.

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Advanced design of UV waveplates based on nano-structured thin films

Cited by 2 publications

References 11 publications

Mesomorphic Ceramic Film Fabricated via Blade Coating of a Lyotropic Nematic Liquid Crystal for High-Power Lasers

Mesomorphic Ceramic Film Fabricated via Blade Coating of a Lyotropic Nematic Liquid Crystal for High-Power Lasers

Investigating the Trade‐off between Optical and Mechanical Properties during Constrained Sintering of Mesomorphic Ceramic Films

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